POWRE: Accretion to Rotating Magnetized Stars

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Abstract - Romanova AST 9973366A full-time research program at Cornell University on the theory, simulations, and analysis of observations of plasma accretion to rotating magnetized stars will be carried out. Many accreting stars, for example, compact stars and protostars, are rotating and are deduced to have significant intrinsic magnetic fields. Key observational aspects of these systems, for example, whether the star spins-up or spins-down, are determined by the interaction of accreting matter with the magnetosphere of the star. This problem of accretion to a rotating magnetized star has been of interest to -astronomers for more than a quarter of century, but it still has only a qualitative, controversial solution. The difficulty of this problem arises from the fact that it is a multidimensional magnetohydrodynamic (MHD) flow problem. Progress on it requires two or three- dimensional simulations which are now feasible on computers. Research on the problem of 2D and 3D modeling of accretion to rotating magnetized stars will be carried out in collaboration with faculty members at Cornell University. Two main directions of research are planned: The first is to perform a systematic simulation study and obtain scaling relations for both disk and Bondi-type spherical accretion to rotating magnetized stars for different rotation rates of the star, different stellar magnetic moments, and different accretion rates. In this study an already developed and tested 2D (axisymmetric) MHD code will be used. The code will be used to determine the inflow or outflow of angular momentum to the star. A second direction of the research will be the creation of a parallel version of the 2D code for use on the Cornell Supercomputer, and the development of 3D code for investigation of 3D aspects of accretion: interchange instability and accretion to an inclined rotator. The results of the simulations will be applied to different specific objects: protostars, cataclysmic variables, X-ray pulsars, QPOs, and transient X-ray sources. . The project involves the international collaboration with two professional specialists in numerical MHD from Russia, who will visit Cornell. The results of the research are expected to have broad general interest for specialists not only in astrophysics, but also in geophysics and planetary sciences. The new version of the code will be documented and made available to other interested scientists. This award is supported by funds from the Division of International Programs, the Division of Astronomical Sciences, and the Office of Multidisciplinary Activities in the Directorate of Mathematical and Physical Sciences.